The invention pertains to plugs, and in particular to a self-locking threaded plug that can be used as a borescope plug, a drain plug, an access plug, a chip detector plug, and other similar threaded parts.
In the aircraft engine industry, for example, many engines include double walled structures, such as a compressor, a combustor and the like, where the outer and inner walls are respectively provided with a number of borescope holes or ports. One purpose of the borescope ports is to allow inspection and monitoring of the engine. This may be accomplished by inserting inspection equipment, such as borescopes and/or probes, through the borescope ports.
Each borescope port requires a removable borescope plug to facilitate borescope inspection of the engine components through the borescope port. In addition, the borescope plug also performs a sealing function to prevent the leakage of high pressure and high temperature gas through the borescope port. Typically, the borescope ports are threaded holes in the engine cases and the borescope plugs typically screw into the ports. The borescope plugs are required to incorporate a secondary locking feature to prevent them from loosening and/or falling out while the engine is operation.
The secondary locking feature can include a number of different schemes. For example, safety wire (lock wire), tab washers, and cotter clips have been used in early engine designs. As the engine designs matured, it became obvious that self-locking secondary locking features provided improved reliability and maintainability. Many new engine designs specify self-locking borescope plugs.
Thus, there is a need to provide a self-locking plug that is highly reusable, robust in function, not prone to damage, does not contain sharp edges, does not have loose parts, and does not require special tools, techniques, or knowledge to operate. Additionally, the self-locking plug should be compact, lightweight, and easy to manufacture.